Electric motors typically include a housing and a pair of end frames mounted on the respective ends of the housing. Each end frame includes a bearing for supporting a rotor shaft for rotation about an axis. It is generally desirable to provide a seal for the rotating shaft to prevent contaminants in the surrounding environment from working themselves into contact with the bearings and/or lubricant for the bearings. An important factor that contributes to the operating life of an electric motor is the operating life of the bearings used to support the rotor shaft. If contaminants such as, for example, water, dirt, debris, dust, etc., enter the bearing cavity or other internal cavities of the motor, the operation of the bearings could be adversely affected leading to premature failure of the bearings or of the motor itself. Bearing failures generally require costly repairs to an electric motor or may require replacement of the motor with an entirely new motor.
Electric motors contemplated for use according to the present invention are typically operable in outdoor environments wherein the outer components of the motor are subject to exposure to moisture, dirt, various contaminants or the like. In those situations, it is known to provide various sealing mechanisms between the rotating shaft and the end frame of the motor to prevent external contaminants, particularly water or other liquids, from moving axially along the shaft through the space between the rotating shaft and the end frame and into the interior of the motor housing.
This is also a significant problem for electric motors in pumps used for such things as swimming pools, hot tubs, waste water treatment facilities or other aquatic or fluid transporting/separating apparatuses. In these environments, there is typically provided a sealing device between the pump and the electric motor driving an impeller. On the impeller side of the sealing device, there is typically a fluid, such as water in a swimming pool, under pressure. If the sealing device fails or leaks, the pressurized fluid may be forced through the sealing device and splashed against an exposed outer wall or end frame of the motor through which the motor shaft normally extends. As a result, it is also desirable to have shaft seals in electric motors of this type.
There are several prior mechanisms for sealing an area between a shaft and an end frame of a motor through which the shaft passes. These prior sealing mechanisms include, for example: (1) maintaining a tight tolerance between the end frame and the rotating shaft; (2) positioning a single, generally flat, slinger washer on the rotating shaft near an outer surface of the end frame where the shaft extends through the end frame; or (3) utilizing a standard shaft lip seal assembly.
However, these prior sealing mechanisms either fail to provide adequate protection or, fail to extend motor operating life at a cost that is acceptable to the ultimate consumer.